A problem that the present invention is related to is the following. In most larger cities, tap water is produced in big plants and is transported in piping systems to the consumers. In order to protect the water against risks of infection during the transportation, a certain quantity of chlorine is usually added before the clean water leaves the plant.
A certain quantity of this chlorine is consumed during the way and a certain quantity of is left in the water when it reaches the consumers. The intention of the addition of chlorine is that the chlorine should decompose potentially dangerous organisms and organic impurities in the pipes. When this takes place, chlorinated hydrocarbons of the type chloroform and bromoform are formed. Hence, also these substances are present in a certain quantity in the water that reaches the consumers.
Even if the amount of chlorine and chlorinated hydrocarbons is low in the water, it is known that the two types of impurities are mutagenic also in small doses, and it is therefore an advantage if it is possible to avoid them to as great an extent as possible.
Since long there are different types of filters on the market, by means of which it is possible to clean water from municipal piping or an own well. However, traditional filters that are in the form of fine-meshed nets do not stop volatile substances such as chlorine and chlorinated hydrocarbons. Neither filters that contain ion exchange mass (for instance softeners) manage this.
For this reason, in many places filters containing activated carbon are now used. The disadvantage of activated carbon is that it is difficult to know when the filter is full, and in many examinations it has been found that the activated carbon quickly may lose effect upon an unexpected load increase and in that connection further turn into a refuge, nutrition place and breeding ground for bacteria and pyrogenes.
For this reason, the carbon filter is frequently combined with other methods to a more complicated apparatus where accordingly also pre-filters to stop coarser particles and organic material, ultraviolet-light lamps to kill bacteria, and ion exchangers for picking up ions are included. Such an equipment becomes relatively expensive and works satisfactory only if the exchange of roughing filter, ultraviolet lamps, ion exchange mass and activated carbon is handled accurately. As an alternative to these multi-stage filters, equipment has also been developed based on distillation and the reversed osmosis. None of these methods, advanced per se, is however entirely efficient in removing chlorine and chlorinated hydrocarbons but have to be supplemented with an activated-carbon final filter. Even if the load on this final filter is much smaller than on carbon filters in the previously mentioned multi-stage filters, also these have to be exchanged at regular intervals, and the problem with overload remains.
A simpler way to kill bacteria as well as remove chlorine and chlorinated hydrocarbons and also other volatile substances from water is to boil water in a boiler or open vessel. The disadvantages of this simple method in comparison with what has been mentioned previously are foremost three. A large quantity of water has to be boiled away in order to be sure of getting rid of the volatile impurities, which in the first place entails that water is wasted and in the second place that the possible non-volatile impurities that are present in water are concentrated. The third disadvantage is that the user does not know when a satisfactory result has been attained.
Within the industry, many methods are developed for the separation of liquid from gas, gas from liquid and gas from another gas. The most common principle is the cyclone principle, which is based on a steam/gas/water mixture being centrifuged and the liquid thereby being pressed out of the mixture. A rather similar principle is that the mixture is led through a conduit having many bends, the liquid being stopped by devices of different forms in the bends.
Furthermore, area-enlarging devices are used in such a way that water/gas/steam mixture is sprayed or sprinkled on large plates or is left to run down large sheets or another type of device having a large area, for instance steel wool or plastic balls.
It is also possible to force a gas, for instance air or nitrogen, through the mixture. This gas then drives off or drags along other gases in the mixture. Frequently, a combination of these techniques is used.
A previously known liquid cleaning device of the relevant type is seen in the Swedish patent 518 388, according to which liquid is heated in a vessel having a lower part, provided with heating members, and an upper part intended for the liquid, as well as an inner central tubular riser member for heated liquid rising upward through the riser member, the heated liquid from the upper open end of the riser member by the gravity running back downward through the upper part outside the riser member for renewed heating and vaporization at constant power and time.
Per se, this liquid cleaning device works well. A disadvantage of the liquid cleaning device in the Swedish patent 518 388 is that when the volume of liquid in the product reaches the boiling temperature, the liquid begins to flash at unchanged supply of energy to the cleaning process. This in turn means that the desirable transport of liquid decreases and that a final product that has not been fully cleaned is obtained.